1. Field of the Invention
The present invention relates to a mechanism for sealing a door tight to a door frame in which the door is mounted. More specifically, the present invention is an over-center door latching mechanism for sealing a bifold door tight to the frame in which it is mounted.
2. Description of the Related Art
A typical overhead bifold door assembly, such as that described in U.S. Pat. No. 4,609,027, issued to Keller on Sep. 2, 1986, includes an upper door panel and a lower door panel, with the upper door panel hingedly connected to the lintel or header of the door frame. When in its first, closed position, the panels of the overhead door are vertically aligned and cooperate to close the doorway, while in its second, open position the panels of the overhead door are in a folded, generally horizontal, parallel relation. Generally, a door of the size contemplated by the present invention is movable by a winch mounted to the lower door panel, with the winch having a cable extending to a fixed location above the doorway for vertically raising and lowering the bottom edge of the lower door panel and bringing the overhead door to its closed position.
Various systems have been developed to address the need for a locking mechanism that will securely lock the panels in their closed, vertically aligned position. In the above-mentioned U.S. Pat. No. 4,609,027 issued to Keller, the weight of the motor and winch mounted on the lower door panel were relied on to act as an anchor to provide dead weight to help keep the door closed. However, such an arrangement would not necessarily provide the affirmative latching action desired to maintain securely the overhead door in its closed position.
An example of a latching system is disclosed in U.S. Pat. No. 4,903,747 issued to Johnson on Feb. 27, 1990. The system disclosed in this patent, however, is directed to a device usable with a pair of relatively small, vertically disposed left and right bifold door assemblies used as closet doors, window shutters, or the like, and cooperates with the inner panels of the two bifold door assemblies. Further, the system disclosed in this patent does not operate automatically as a part of the door opening and closing operation.
Another example of a latching mechanism is disclosed in U.S. Pat. No. 4,637,446 issued to McQueen et al. on Jan. 20, 1987, which shows a spring biased latching system. The system disclosed in this patent shows a latch member that engages a catchplate mounted on the door track. Opening and closing of the door is done manually, however, with a lift cable being used to disengage the latch member from the catchplate.
U.S. Pat. No. 5,168,914, also issued to Keller, discloses a latching assembly, which includes a latch arm cooperating with a latch member affixed to an adjacent doorjamb. The latching mechanism of U.S. Pat. No. 5,168,914 includes a latch shaft that is rotatably mounted to a latch bracket which is itself attached to the door. A latch arm is affixed to one end of the latch shaft so as to be able to engage the latch member secured to the door jamb to which the door is mounted. The opposite end of the latch shaft has affixed thereto a first tensioning arm, which is arranged generally parallel to the latch arm secured to the opposite end of the latch shaft. The latch shaft is spring biased so that the latch arm is normally rotated away from the latch member secured to the doorjamb. An actuation assembly is operatively connected to the latching mechanism by a cable secured to the tensioning arm of the latching mechanism. In order to securely latch and latching mechanism, the actuation assembly applies tension to the cable secured to the tensioning arm which in turn transmits a moment to the latch arm, thereby rotating the latch arm downward and into contact with the latch member affixed to the doorjamb. The force exerted upon the latching member secured to the doorjamb by the latch arm acts to pull the door panel into contact with the door jamb thereby latching and sealing the door.
A door latching mechanism manufactured and marketed by Schweiss Distributing, Inc. of Fairfax, Minn. comprises a latch arm which is pivotally mounted to a panel of a bifold door. This latch arm contacts a latch member substantially at the distal end of the latch arm. The latch arm of the Schweiss mechanism is urged into contact with the latch member secured to the doorjamb by a cable and pulley arrangement coupled to the latch arm also substantially at the distal end thereof. Because the point of contact between the latch arm and the latch member attached to the doorjamb is at substantially the same location as the point of connection for the cable and pulley system to the latch arm, i.e. at the distal end of the latch arm, the Schweiss door latching mechanism operates by main force alone and does not realize a mechanical advantage.
Accordingly, it is an object of this invention to provide a mechanism for securely locking and sealing a door such as a bifold door to the door frame in which the door has been mounted. In addition, it is an object of this invention to provide a door sealing mechanism that may be actuated by a number of distinct actuation mechanisms. Finally, it is an object of this invention to provide a door sealing mechanism which applies a sealing force to a door which is substantially normal to the plane of the door and which utilizes the mechanical advantage of a lever to limit the magnitude of forces which must be applied to the latching mechanism by a chosen actuation mechanism.
These and other objectives and advantages of the invention will appear more fully from the following description, made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views.
The door closing mechanism of the present invention includes a latch arm assembly and an actuation mechanism or assembly. The latch arm assembly includes a latch arm that is pivotally secured to a panel of a bifold door. The latch arm is pivotable between a first, open position and a second, latched position. A latch member is secured to the jamb of the door frame to which the door frame is mounted. The latch member is mounted to the jamb adjacent to where the latch arm assembly is mounted to the door panel so that the latch arm may engage the latch member when the latch arm is in its second, latched position. A spring biasing mechanism is preferably connected between the door panel and the latch arm to bias the latch arm towards its first, open position.
A bracket having a pivot pin is used to secure the latch arm to the panel of the bifold door. In a preferred embodiment of the present invention, an offset arm or bar, rather than the latch arm itself, is rotatably mounted on the bracket pivot pin with the latch arm being secured to the distal end of the offset arm.
In order to realize the mechanical advantage present in the latch arm assembly, the latch member, which may comprise a rigid bracket or roller bearing affixed to the door jamb in which the door is mounted, is located such that the latch arm contacts the bracket along a first half of the latch arm nearest the pivot point of the latch arm. In some applications of the present invention, it may be preferred to have the latch arm contact the latch member bracket along the first third of the latch arm nearest the pivot point of the latch arm.
It is preferred to arrange and construct the latch member so that when the latch arm is moved into its second, closed position, the force exerted upon the latch member by the latch arm is substantially normal to the plane of the door so as to cause the door to contact the door frame over substantially its entire height. In addition, it is preferable that the latch arm be substantially parallel to the panel of the bifold door when in its second, latched position.
The connecting means is the operative connection between the actuation mechanism and the latch arm assembly and transmits the motive power that moves the latch arm from the actuation mechanism to the latch arm assembly. The actuation mechanism which is used to move the latch arm between its first and second positions may comprise a hand-operated winch or a lever arm that is pivotally secured to a panel of the bifold door. Another embodiment of the actuation mechanism includes a cylindrical threaded portion having a first end and a second end with the cylindrical threaded portion being co-axial with, and secured to, a power shaft mounted upon the door for raising and lowering the door. The power shaft is operatively connected to a motor for rotating the power shaft. A threaded nut travels along the cylindrical threaded portion and has a connecting arm projecting therefrom. The connecting arm is attached to the connecting means which in turn connects to the latch arm assembly. A stopping segment is located near an end of the cylindrical threaded portion for the purpose of confronting the threaded nut which travels along the cylindrical threaded portion. When the threaded nut confronts the stopping segment, the threaded nut, and hence the connecting arm, rotate with the power shaft to actuate the latch arm assembly.